Magnetic field shielding sheet for a wireless charger, method for manufacturing same, and receiving apparatus for a wireless charger using the sheet

ABSTRACT

Provided are a magnetic field shield sheet for a wireless charger, a method of manufacturing the sheet, and a receiver for the wireless charger by using the sheet. The sheet includes at least one layer thin magnetic sheet made of an amorphous ribbon separated into a plurality of fine pieces; a protective film that is adhered on one surface of the thin magnetic sheet via a first adhesive layer provided on one side of the protective film; and a double-sided tape that is adhered on the other surface of the thin magnetic sheet via a second adhesive layer provided on one side of the double-sided adhesive tape, wherein gaps among the plurality of fine pieces are filled by some parts of the first and second adhesive layers, to thereby isolate the plurality of fine pieces.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/366,439, which is the U.S. national stage of InternationalApplication No. PCT/KR2012/011256, filed Dec. 21, 2012, which claimspriority to Korean Patent Application No. 10-2011-0138987, filed Dec.21, 2011. The foregoing applications are incorporated herein byreference.

TECHNICAL FIELD

The present invention relates to a magnetic field shield sheet for awireless charger, a method of manufacturing the magnetic field shieldsheet, and a receiver for the wireless charger by using the magneticfield shield sheet, and more particularly to, a magnetic field shieldsheet for a wireless charger, which blocks an effect of analternating-current magnetic field generated when a charger function fora portable mobile terminal device is implemented in a non-contactwireless manner on a main body of the portable mobile terminal deviceand exhibits excellent electric power transmission efficiency, a methodof manufacturing the magnetic field shield sheet, and a receiver for thewireless charger by using the magnetic field shield sheet.

BACKGROUND ART

As methods of charging secondary batteries mounted in electronicequipment such as portable terminals and video cameras, there are twotypes of charging methods, i.e., a contact type charging method and anon-contact type charging method. The contact type charging methodcarries out a charging operation by making an electrode of a powerreception device in direct contact with an electrode of a power feedingdevice.

The contact type charging method is commonly used in a wide range ofapplications, since a structure of a device implementing the contacttype charging method is simple. However, in association withminiaturization and weight reduction of electronic equipment, variouselectronic devices become light in the weight thereof, and accordingly alow contact pressure between electrodes of the power reception deviceand the power feeding device may cause problems such as charge failurecharge error. Further, secondary batteries are weak at heat, which needsto prevent the temperature rise of the batteries, and to pay attentionto a circuit design so as not to cause overcharge and overdischarge. Tocope with these problems, a non-contact type charging method is beingconsidered in recent years.

The non-contact type charging method is a charging method using anelectromagnetic induction principle in which coils are mounted at bothsides of the power reception device and the power feeding device.

A non-contact type charger can be miniaturized by putting a ferrite coreto be in a magnetic core and winding coils around the ferrite core.Furthermore, for miniaturization and reduction in thickness, a techniqueof forming a resin substrate by mixing ferrite powder and amorphouspowder and mounting a coil and the like on the resin substrate, has beenproposed. However, in the case that a ferrite sheet is processed thinly,the thinly processed ferrite sheet may be easily broken and weak inimpact resistance. As a result, there have been problems that defectshave occurred in the power reception device due to a fall or collisionof the non-contact type charger.

Further, in order to reduce thickness of a power reception portion of anelectronic device in response to reduction in the thickness of theelectronic device, a planar coil that is formed by printing a metalpowder paste as a coil have been employed. A structure of strengtheninga coupling of a planar coil and a magnetic sheet has been proposed. Inthe proposed structure, a magnetic body or a magnetic sheet is used as acore material to strengthen the coupling between primary and secondarycoils.

Meanwhile, if a power transmission speed increases, defects betweenadjacent transformers, as well as defects caused by heat from thesurrounding components, may be likely to occur. That is, in the casethat the planar coils are used, the magnetic flux passing through theplanar coils is connected to a substrate or the like inside anelectronic device, an internal portion of the electronic device may beheated due to eddy currents caused by electromagnetic induction. As aresult, large power cannot be transmitted and thus a time-consumingproblem may be caused for charging the electronic device.

To cope with this problem, a magnetic body or a magnetic sheet was usedas a shielding member on the back of the substrate. In order to obtain asufficient shielding effect, as the magnetic body or the magnetic sheetmay have the larger magnetic permeability, and the larger area andthickness, a more effective shielding effect can be obtained.

In general, a magnetic body such as an amorphous ribbon, a ferritesheet, or a polymer sheet containing magnetic powder is used as themagnetic field shield sheet. An effect of focusing a magnetic field forimproving magnetic field shielding performance and additional featuresmay be good in the order of amorphous ribbons, a ferrite sheet, and apolymer sheet containing magnetic powder, with high magneticpermeability.

In the case of a power reception device of a conventional non-contacttype charging system, a magnetic body or a magnetic sheet with highmagnetic permeability and large volume is disposed on the oppositesurface to a primary coil side, i.e., on the surface of a secondarycoil, for reinforcement of a coupling for improving transmissionefficiency, and for improving a shielding performance for suppression ofheat generation. According to this arrangement, fluctuations in theinductance of the primary coil become large, and an operation conditionof a resonant circuit is shifted from a resonance condition at which asufficient effect can be exhibited according to a relative positionalrelationship between the magnetic body and the primary coil.

Korean Patent Application Publication No. 10-2010-31139 provides a powerreception device for improving a resonance performance and alsosuppressing heat generation to solve the aforementioned problems, andproposes a technique of enabling large transmission power and shorteningcharge time, through an the electronic device and a power receptionsystem using the power reception device.

In other words, according to Korean Patent Application Publication No.10-2010-31139, a composite magnetic body including a plurality ofmagnetic sheets magnetic ribbons are arranged at at least one locationbetween a spiral coil a power reception-side spiral coil: a secondarycoil and a secondary battery, and between a rectifier and the spiralcoil, to thereby prevent a magnetic flux generated from the powerreception-side spiral coil from interlinking a circuit board and asecondary battery, and to thereby suppress noise and heat generationcaused by an induced electromotive force electromagnetic induction, andthe amount of fluctuation of inductance in the primary coil iscontrolled due to presence or absence of the secondary coil to thusenhance a resonance performance of a resonant circuit constituted by theprimary coil and to thereby effectively control oscillation.

The composite magnetic body is set so that first magnetoresistance of afirst magnetic sheet adjacent to the spiral coil is less than or equalto 60, second magnetoresistance of a second magnetic sheet laminated onthe first magnetic sheet is greater than or equal to 100, and a value ofthe second magnetoresistance divided by the first magnetoresistance isequal to or greater than 1.0.

The first magnetic sheet is prepared by bonding polycarbonate resins onboth surfaces of a first amorphous ribbon by using adhesive layers,respectively, and the second magnetic sheet is prepared by bondingpolycarbonate resins on both surfaces of a second amorphous ribbon withlarge relative permeability by using adhesive layers, respectively.Then, the first magnetic sheet and the second magnetic sheet areintegrally bonded via an adhesive layer.

Meanwhile, the ferrite sheet or a polymer sheet containing magneticpowder has the magnetic permeability a little lower than the amorphousribbon, and thus in order to improve the performance of such lowmagnetic permeability, thickness of the ferrite sheet or a polymer sheetbecomes large compared to the thin amorphous ribbon of several tens μm.Therefore, it is difficult to respond to a thinning tendency ofterminals.

Further, in the case of amorphous ribbon with high magneticpermeability, the ribbon itself is a metal thin plate, and thus there isno burden on thickness of the amorphous ribbon. However, when analternating-current magnetic field according to frequency of 100 kHzused for power transmission is applied to the amorphous ribbon,functionality of applications may be reduced due to an influence of eddycurrents of the ribbon surface, or problems of reducing wirelesscharging efficiency and causing heat generation may occur.

Co-based or Fe-based amorphous ribbons can increase surface resistanceslightly, through heat treatment. However, in the case that a processingtreatment such as a flake treatment process of reducing a surface areaof the ribbon is performed in order to further reduce the eddy currenteffects, the magnetic permeability is significantly degraded and thefunction as the shield sheet is greatly degraded.

Also, most of wireless chargers employ a structure of adopting permanentmagnets that assist an alignment with a power receiver in a powertransmitter for power transmission, in order to increase the powertransfer efficiency of the chargers to the maximum. A magnetization orsaturation phenomenon occurs in a thin shield sheet due to adirect-current magnetic field of the permanent magnets, to therebydecrease the performance of the chargers or sharply decreasing the powertransmission efficiency.

Accordingly, in the case of the conventional chargers, the thickness ofthe shield sheet must be quite thick in the order of 0.5 T or higher, inorder to indicate shielding features without being affected by thepermanent magnets, and to maintain high power transmission efficiency,which may cause a major obstacle on slimming of portable terminals.

A voltage induced in a secondary coil of a wireless charger isdetermined by the Faraday's law and the Lenz's law, and thus it is moreadvantageous to have the greater amount of magnetic flux linked with thesecondary coil in order to obtain a high voltage signal. The amount ofthe magnetic flux becomes large as the amount of a soft magneticmaterial contained in the secondary coil becomes large and the magneticpermeability of the material becomes high. In particular, since thewireless chargers essentially employ a non-contact power transmissionsystem, a magnetic field shield sheet in which the secondary coil ismounted is needed to be made of a magnetic material with highpermeability, in order to focus wireless electromagnetic waves made fromthe primary coil of a power transmission device, on the secondary coilof a power reception device.

Conventional magnetic field shield sheets for wireless chargers do notpresent solutions for attaining the thin film but solving the heatgeneration problem due to shields and improving the wireless chargingefficiency. Thus, the present inventors recognized that inductance(magnetic permeability) is less reduced and magnetoresistance is greatlyreduced, although an amorphous ribbon undergoes flakes in the case ofthe amorphous ribbon, and thus a quality factor (Q) of the secondarycoil is increased, to thereby reach the present invention.

DISCLOSURE Technical Problem

To solve the above problems or defects, it is an object of the presentinvention to provide a magnetic field shield sheet for a wirelesscharger, which greatly reduces a loss due to eddy currents by a flaketreatment process of an amorphous ribbon, to thereby block an effect ofa magnetic field influencing upon a main body and a battery of aportable mobile terminal device and simultaneously to increase a qualityfactor (Q) of a secondary coil, and to thus exhibit excellent electricpower transmission efficiency, a method of manufacturing the magneticfield shield sheet, and a receiver for the wireless charger by using themagnetic field shield sheet.

It is another object of the present invention to provide a magneticfield shield sheet for a wireless charger, which fills a gap betweenfine pieces of an amorphous ribbon through a flake treatment process ofthe amorphous ribbon and then a compression laminating process with anadhesive, to thereby prevent water penetration, and which simultaneouslysurrounds all surfaces of the fine pieces with an adhesive (or adielectric) to thus mutually isolate the fine pieces to thereby promotereduction of eddy currents and prevent shielding performance fromfalling, and a manufacturing method thereof.

It is still another object of the present invention to provide amagnetic field shield sheet for a wireless charger, which establishes ashape of a shield sheet into a shape similar to that of a secondary coilof a receiving device for a wireless charger, to thereby exhibit highpower transmission efficiency even though a small number of nanocrystalline ribbons are used, and a power reception device using themagnetic field shield sheet.

It is yet another object of the present invention to provide a magneticfield shield sheet for a wireless charger, which sequentially performs aflake treatment process and a laminating process by using a roll-to-rollmethod, to thereby achieve a sheet molding process to thus maintainoriginal thickness of the sheet and to thus exhibit high productivityand inexpensive manufacturing costs.

Technical Solution

To accomplish the above and other objects of the present invention,according to an aspect of the present invention, there is provided amagnetic field shield sheet for a wireless charger, the magnetic fieldshield sheet comprising:

at least one layer thin magnetic sheet made of an amorphous ribbonseparated into a plurality of fine pieces;

a protective film that is adhered on one surface of the thin magneticsheet via a first adhesive layer provided on one side of the protectivefilm; and

a double-sided tape that is adhered on the other surface of the thinmagnetic sheet via a second adhesive layer provided on one side of thedouble-sided adhesive tape,

wherein gaps among the plurality of fine pieces are filled by some partsof the first and second adhesive layers, to thereby isolate theplurality of fine pieces.

According to another aspect of the present invention, there is provideda method of manufacturing a magnetic field shield sheet for a wirelesscharger, the method comprising the steps of:

adhering a protective film and a double-sided tape formed of a releasefilm on an exposed surface of the double-sided tape, on both sides of atleast one layer thin magnetic sheet made of an amorphous ribbon, tothereby form a laminate sheet;

performing a flake treatment process of the laminate sheet to thusseparate the thin magnetic sheet into a plurality of fine pieces; and

laminating the flake treated laminate sheet, to thus fill some parts offirst and second adhesive layers provided in the protective film and thedouble-sided tape into gaps among the plurality of fine pieces,

a protective film that is adhered on one surface of the thin magneticsheet via a first adhesive layer provided on one side of the protectivefilm; and

a double-sided tape that is adhered on the other surface of the thinmagnetic sheet via a second adhesive layer provided on one side of thedouble-sided adhesive tape, together with flattening and thinning of thelaminate sheet, and to thereby isolate the plurality of fine pieces.

According to still another aspect of the present invention, there isprovided a reception device for a wireless charger that charges asecondary battery by an electromagnetic induction method from atransmission device for the wireless charger, the reception devicecomprising:

a secondary coil that receives a wireless high frequency signaltransmitted by the electromagnetic induction method from thetransmission device; and

a magnetic field shield sheet that is disposed between the secondarycoil and the secondary battery, and that shields a magnetic fieldgenerated by the wireless high frequency signal and simultaneouslyinduces the secondary coil to absorb the wireless high frequency signalnecessary to perform a wireless charging function,

wherein the magnetic field shield sheet comprises:

at least one layer thin magnetic sheet made of an amorphous ribbonseparated into a plurality of fine pieces;

a protective film that is adhered on one surface of the thin magneticsheet via a first adhesive layer provided on one side of the protectivefilm; and

a double-sided tape that is adhered on the other surface of the thinmagnetic sheet via a second adhesive layer provided on one side of thedouble-sided adhesive tape,

wherein gaps among the plurality of fine pieces are filled by some partsof the first and second adhesive layers, to thereby isolate theplurality of fine pieces.

Advantageous Effects

As described above, the present invention provides a magnetic fieldshield sheet for a wireless charger, which greatly reduces a loss due toeddy currents by a flake treatment process of an amorphous ribbon, tothereby block an effect of a magnetic field influencing upon a main bodyand a battery of a portable mobile terminal device and simultaneously toincrease a quality factor (Q) of a secondary coil, and to thus exhibitexcellent electric power transmission efficiency, a method ofmanufacturing the magnetic field shield sheet, and a receiver for thewireless charger by using the magnetic field shield sheet.

In addition, the present invention provides a magnetic field shieldsheet for a wireless charger, which fills a gap between fine pieces ofan amorphous ribbon through a flake treatment process of the amorphousribbon and then a compression laminating process with an adhesive, tothereby prevent water penetration, and which simultaneously surroundsall surfaces of the fine pieces with an adhesive (or a dielectric) tothus mutually isolate the fine pieces to thereby promote reduction ofeddy currents and prevent shielding performance from falling, and amanufacturing method thereof. As a result, all surfaces of the finepieces are surrounded by an adhesive (or a dielectric material) tothereby prevent water from penetrating into the amorphous ribbon and tothus prevent the amorphous ribbon from being oxidized and changes inappearance and characteristics from being deteriorated.

Moreover, the present invention provides a magnetic field shield sheetfor a wireless charger, which establishes a shape of a shield sheet intoa shape similar to that of a coil of a receiving device for a wirelesscharger, to thereby exhibit a high power transmission efficiency orequal power transmission efficiency while lowering thickness of themagnetic field shield sheet to be equal to or less than 0.3 mm, eventhough a small number of nanocrystalline ribbons are used, and a powerreception device using the magnetic field shield sheet.

In addition, the present invention provides a magnetic field shieldsheet for a wireless charger, which sequentially performs a flaketreatment process and a laminating process by using a roll-to-rollmethod, to thereby achieve a sheet molding process to thus maintainoriginal thickness of the sheet and to thus exhibit high productivityand inexpensive manufacturing costs.

DESCRIPTION OF DRAWINGS

FIG. 1 is an exploded perspective view showing a magnetic field shieldsheet for a wireless charger according to the present invention.

FIG. 2 is a cross-sectional view showing an example of using one pieceof nanocrystalline ribbon sheet according to a first embodiment of thepresent invention.

FIG. 3 is a cross-sectional view showing an example of using six piecesof nanocrystalline ribbon sheets according to a second embodiment of thepresent invention.

FIGS. 4 and 5 are cross-sectional views showing the structure of aprotective film and a double-sided tape that are respectively used inthe present invention.

FIG. 6 is an exploded perspective view showing a magnetic field shieldsheet for a wireless charger according to a third embodiment of thepresent invention.

FIG. 7 is a flowchart view for describing a process of manufacturing amagnetic field shield sheet for a wireless charger according to thepresent invention.

FIGS. 8 and 9 are cross-sectional views showing a flake treatmentprocess of a laminate sheet according to the present invention,respectively.

FIG. 10 is a cross-sectional view showing a state where a laminate sheetis flake-processed according to the present invention.

FIGS. 11 and 12 are cross-sectional views showing a laminating processof a flake-treated laminate sheet according to the present invention,respectively.

FIG. 13 is a cross-sectional view showing a state where a magnetic fieldshield sheet for a wireless charger according to a first embodiment ofthe present invention has been flake-processed and then laminated.

FIG. 14A is an enlarged photograph of a magnetic field shield sheet thathas not passed through a laminating process after having performed aflake treatment process, but has undergone a humidity test, and FIG. 14Bis an enlarged photograph of a magnetic field shield sheet that haspassed through a laminating process after having performed a flaketreatment process and has undergone a humidity test.

FIGS. 15A and 15B are a cross-sectional view and a plan view showing athin magnetic sheet that is used in a magnetic field shield sheet for awireless charger according to a fourth embodiment of the presentinvention.

FIG. 16 is an exploded perspective view showing a structure that amagnetic field shield sheet according to the present invention isapplied to a reception device for a wireless charger.

FIG. 17 is an exploded perspective view showing that the receptiondevice for a wireless charger of FIG. 16 is assembled with a batterycover and coupled with a portable terminal.

FIG. 18 is a plan view showing a dual-antenna structure in which anantenna for near field communications (NFC) and an antenna for awireless charger are formed by using a flexible printed circuit board(FPCB).

FIG. 19 is a schematic diagram showing a measuring structure for testingthe efficiency and temperature characteristics of a magnetic fieldshield sheet according to the present invention.

BEST MODE

The above and other objects, features, and advantages of the presentinvention can be appreciated by the following description and will beunderstood more clearly by embodiment of the present invention. Inaddition, it will be appreciated that the objects and advantages of thepresent invention will be easily realized by means shown in the appendedpatent claims, and combinations thereof. Accordingly, the technicalspirit of the present invention can be easily implemented by one ofordinary skill in the art.

Further, if it is determined that the detailed description of the knownart related to the present invention makes the gist of the presentinvention unnecessarily obscure, a detailed description thereof will beomitted.

FIG. 1 is an exploded perspective view showing a magnetic field shieldsheet for a wireless charger according to the present invention, andFIG. 2 is a cross-sectional view showing an example of using one pieceof nanocrystalline ribbon sheet according to a first embodiment of thepresent invention.

Referring to FIGS. 1 and 2, a magnetic field shield sheet 10 for awireless charger according to the present invention includes: at leastone layer (or a multi-layer) thin magnetic sheet 2 separated and/orcracked into a plurality of fine pieces 20, by thermally treating anamorphous alloy ribbon or nanocrystalline alloy ribbon and thenperforming a flake treatment process; a protective film 1 that isadhered on an upper portion of the thin magnetic sheet 2; a double-sidedtape 3 that is adhered on a lower portion of the thin magnetic sheet 2;and a release film 4 that is separably adhered on a lower portion of thedouble-sided tape 3.

For example, a thin ribbon made of an amorphous alloy or nanocrystallinealloy may be used as the thin magnetic sheet 2.

A Fe-based or Co-based magnetic alloys may be used as the amorphousalloy, and considering the material cost, the Fe-based magnetic alloysare preferably used.

For example, Fe—Si—B alloys may be used as the Fe-based magnetic alloys.Here, it is preferable that the content of Fe is 70-90 atomic % (whichwill be abbreviated as at %), and the content of a sum of Si and B is10-30 at %. The higher content of Fe and other metals may be, the higherthe saturation magnetic flux density may be, but when the content of Feis excessive, it is difficult to form an amorphous state. Thus, thecontent of Fe in the present invention is preferably 70-90 at %. Inaddition, when the content of the sum of Si and B is in the range of10-30 at %, an amorphous forming capability of an alloy is the mostexcellent. In order to prevent corrosion, corrosion resistant elementssuch as Cr and Co can be added within 20 at % into this basiccomposition, and if necessary, other metallic elements may be includedin small quantities in the basic composition to impart differentproperties.

The Fe—Si—B alloys can be used; for example, the crystallizationtemperature of a certain Fe—Si—B alloy is 508° C., and the Curietemperature (Tc) thereof is 399° C. However, the crystallizationtemperature can be varied depending on the content of Si and B, or theother metal elements and the content thereof added in addition toternary alloy elements.

A Fe-based amorphous alloy, for example, a Fe—Si—B—Co-based alloy may beused according to the required conditions, in the present invention.

Meanwhile, a thin ribbon made of a Fe-based nanocrystalline magneticalloy can be used as the thin magnetic sheet 2.

An alloy satisfying the following Equation 1 is preferably used as theFe-based nanocrystalline magnetic alloy.Fe_(100-c-d-e-f-g)A_(c)D_(d)E_(e)Si_(f)B_(g)Z_(h)  Equation 1

In Equation 1, an element A is at least one element selected from Cu andAu, an element D is at least one element selected from Ti, Zr, Hf, V,Nb, Ta, Cr, Mo, W, Ni, Co, and rare earth elements, an element E is atleast one element selected from Mn, Al, Ga, Ge, In, Sn, and platinumgroup elements, an element Z is at least one element selected from C, N,and P, c, d, e, f, g, and h are numbers that satisfy the followingrelational expressions 0.01≤c≤8 at %, 0.01≤d≤10 at %, 0≤e≤10 at %,10≤f≤25 at %, 3≤g≤12 at %, 15≤f+g+h≤35 at %, respectively, and the alloystructure of an area ratio of 20% or more is formed of the finestructure of the particle size of equal to or less than 50 nm.

In the aforementioned Equation 1, the element A is used to enhancecorrosion resistance of the alloy, to prevent coarsening of crystalgrains and at the same time, improve the magnetic properties such as theiron loss and the permeability of the alloy. When the content of theelement A is too small, it is difficult to obtain the effect ofsuppressing coarsening of crystal grains. Conversely, when the contentof the element A is excessively large, the magnetic properties aredegraded. Thus, it is preferable that the content of the element A is inthe range from 0.01 to 8 at %. The element D is an element that iseffective for the uniformity of the crystal grain diameter, thereduction of magnetostriction, etc. It is preferable that the content ofthe element D is in the range from 0.01 to 10 at %.

The element E is an element that is effective for the soft magneticproperties of the alloy and improvement of corrosion resistance of thealloy. The content of the element E is preferably not more than 10 at %.The elements Si and B are elements that make the alloy to becomeamorphous at the time of producing the magnetic sheet. It is preferablethat the content of the element Si is in the range from 10 to 25 at %,and it is preferable that the content of the element B is in the rangefrom 3 to 12 at %. In addition, it may include the element Z as anelement that makes the alloy to become amorphous, other than Si and B.In that case, the total content of the elements Si, B and Z ispreferably in the range of 15 to 35 at %. It is preferable to implementthe microcrystalline structure that crystal grains whose grain diametersare in the range of 5 to 30 nm exist in the range of 50 to 90% as anarea ratio in the alloy structure.

Further, a Fe—Si—B—Cu—Nb alloy can be used as a Fe-based nanocrystallinemagnetic alloy that is used in the thin magnetic sheet 2, and in thiscase, it is preferable that the content of Fe is 73-80 at %, the contentof the sum of Si and B is 15-26 at %, and the content of the sum of Cuand Nb is 1-5 at %. An amorphous alloy that is obtained by producingsuch a composition range in the form of a ribbon can be easilyprecipitated into nanocrystalline grains by a thermal treatment to bedescribed later.

As shown in FIG. 4, the protective film 1 may be implemented by using aresin film 11 including a polyethylene terephthalate (PET) film, apolyimide film, a polyester film, polyphenylene sulfade (PPS) film, apolypropylene (PP) film, or a fluorine resin-based film such as polytetra fluoroethylene (PTFE), and is attached to one side of the thinmagnetic sheet 2 through a first adhesive layer 12.

Further, the protective film 1 is 1 to 100 μm, in thickness, and it ispreferably in the range of 10-30 μm, and it is more preferable to have athickness of 20 μm.

When the protection film 1 used in the present invention 1 is attachedon one side of the amorphous ribbon sheet that is used as the thinmagnetic sheet 2, a release film 4 a attached on the other surface ofthe first adhesive layer 12 to protect the first adhesive layer 12 isremoved and then the protection film 1 is attached on one side of theamorphous ribbon sheet.

Further, as shown in FIG. 5, the double-sided tape 3 is formed of a basemember 32 made of a fluorine resin-based film, for example, a PET(Polyethylene Terephthalate) film, on both sides of which second andthird adhesive layers 31 and 33 are formed. Release films 4 and 4 b areattached on the outer surfaces of the second and third adhesive layers31 and 33, respectively. The release films 4 and 4 b are integrallyformed in the manufacture of the double-sided tape 3, and are peeled offand removed when the magnetic field shield sheet 10, 10 a, or 10 b isattached on an electronic device.

As illustrated in FIG. 3, in order to interconnect a plurality ofamorphous ribbon sheets 21-26, all release films 4 and 4 b of FIG. 5 areremoved from both sides of double-sided tapes 3 a-3 f interposed betweenthe amorphous ribbon sheets 21-26.

The double-sided tapes 3 and 3 a-3 f may be a type of including a basemember as described above, but may be a type of including no base memberbut being formed of only adhesive layers. In the case of thedouble-sided tapes 3 a-3 f interposed between the amorphous ribbonsheets 21-26, it is preferable to use no-base type double-sided tapes interms of a thinning process.

The first to the third adhesive layers 12, 31, and 33 may be implementedby using, for example, acrylic adhesives, but may be of course possiblyimplemented by using different types of adhesives, as illustrated inFIG. 2.

The double-sided tapes 3 and 3 a-3 f may have 10, 20, 30 μm thick,preferably have a thickness of 10 μm.

One piece of the thin magnetic sheet 2 that is used for the shield sheet10, 10 a or 10 b may have a thickness of 15 to 35 μm for example. Inthis case, in consideration of a handling process after the heattreatment of the thin magnetic sheet 2, a thickness of the thin magneticsheet 2 is preferably set to be in the range of 25 to 30 μm. The thinnerthe thickness of the ribbon may be, a breakage phenomenon of the ribbonmay occur due to even a little shock at the time of performing ahandling process after the heat treatment.

Meanwhile, when a reception device for a wireless charger is mounted andused in a battery cover 5 of a mobile terminal device 101 of FIG. 17, asecondary coil (reception coil) 6 is attached to and used for a magneticfield shield sheet 10 as illustrated in FIGS. 16 and 17, in the case ofthe magnetic field shield sheet 10. In this case, the secondary coil 6forms a resonant circuit and therefore, the shield sheet 10 influenceson inductance of the resonant circuit formed by the secondary coil(receiving coil) 6.

In this case, the magnetic filed shield sheet 10 serves as an inductorthat plays a role of shielding a magnetic field to block effects of awireless power signal from a transmission device on the portableterminal 101 and simultaneously plays a role of guiding the wirelesspower signal to be received at the secondary coil of the receptiondevice 6 in high efficiency.

Preferably, the thin magnetic sheet 2 is separated into a plurality offine pieces 20 through a flake treatment process, and the plurality offine pieces 20 have a size of several tens of micrometers (μm) to equalto or less than three (3) mm.

In the case that the thin magnetic sheet 2 is flake-processed andseparated into a plurality of fine pieces 20, reduction of a value ofthe inductance (L) of the magnetic sheet is achieved larger thanreduction of the magnetoresistance (R) of the magnetic sheet. As aresult, if the thin magnetic sheet 2 is made to be flake-processed, aquality factor (Q) of the resonant circuit formed by the secondary coilof the reception device 6 is increased, and thus power transmissionefficiency is increased.

Further, in the case that the thin magnetic sheet 2 is separated into aplurality of fine pieces 20, the heat generation problem of the batterycan be blocked by reducing losses due to eddy currents.

Furthermore, in the case that a thin magnetic sheet 2 a is flaked in thepresent invention as shown in FIG. 10 and then a thin magnetic sheet 2is laminated as shown in FIG. 13, parts of first and second adhesivelayers 12 and 31 penetrate into gaps 20 a of FIG. 10 between theplurality of fine pieces 20. Accordingly, the plurality of fine pieces20 are isolated as adhesives that act as dielectrics.

As a result, in the case that only a flake treatment process is simplydone, the fine pieces 20 are in contact with each other according toflow of the fine pieces 20, and thus the size of the fine pieces 20increases to thereby cause a problem of increasing the eddy currentlosses, but block the problem from occurring, since the whole surface ofthe fine pieces 20 is surrounded by the dielectric, through thelaminating process.

As shown in FIG. 2, a magnetic field shield sheet 10 a for a wirelesscharger according to a first embodiment of the present invention has astructure that one amorphous ribbon sheet 21 is used in which aprotective film 1 is bonded on one side of the amorphous ribbon sheet21, and a release film 4 is bonded via a double-sided tape 3 on theother side of the amorphous ribbon sheet 21.

Further, a magnetic field shield sheet 10 b according to a secondembodiment of the present invention as illustrated in FIG. 3, a numberof amorphous ribbon sheets 21-26 are laminated and used as a thinmagnetic sheet to increase the quality factor Q and the power transferefficiency of the secondary coil 6.

A permanent magnet to assist an alignment with the reception device canbe adopted in the power transmission device in the wireless charger inorder to enhance efficiency of the charger at maximum. That is, acircular permanent magnet is provided inside a primary coil(transmission coil) of the transmission device, and thus the exactalignment of the reception device overlying the transmission device isachieved to thereby hold the reception device to be stuck.

Accordingly, the magnetic field shield sheet for a wireless charger isrequired to shield both alternating-current (AC) magnetic fields thatare generated by the power transfer of a frequency of 100 KHz to 150 KHzfrom the transmission device, as well as direct-current (DC) magneticfields that are generated by the permanent magnets.

By the way, since the DC magnetic fields influence upon the magneticfield shield sheet 10, greater than the AC magnetic fields, the thinshield sheet is magnetically saturated to thereby cause problems ofdropping a shielding performance as the shield sheet or sharply reducingpower transmission efficiency.

Thus, in the case that the permanent magnet is employed in thetransmission device of the wireless charger, it is required to determinethe amorphous ribbon sheets 21-26 to be laminated by taking into accounta number of layers whose magnetic saturation is achieved by thepermanent magnet.

In addition, the Fe-based amorphous alloys are greater than thenanocrystalline alloys in view of the saturation field. Accordingly, inthe case that amorphous ribbon sheets 21-26 made of the Fe-basedamorphous alloys are used, 2 to 8 layers can be used by stacking one onanother. For example, using 3 to 5 layers is preferably to obtain highmagnetic permeability. In this case, the inductance of the laminatesheet (i.e., permeability) is preferably in the range of about 13 μH to19 μH.

Further, in the case that the amorphous ribbon sheets 21-26 made ofnanocrystalline alloy are used, 4 to 12 layers are laminated to then beused, for example, it is preferable to use 7 to 9 layers to obtain highmagnetic permeability. In this case, the inductance of the laminatesheet (i.e., permeability) is preferably in the range of about 13 μH to21 μH.

Meanwhile, in the case that no permanent magnet is adopted in thetransmission device of the wireless charger, it is possible to use arelatively small number of amorphous ribbon sheets when compared withthe case of employing permanent magnets.

In this case, in the case that amorphous ribbon sheets made of theFe-based amorphous alloys or nanocrystalline alloys are used, 1 to 4layers are laminated to then be used. In this case, the inductance ofthe laminate sheet (i.e., permeability) is preferably in the range ofabout 13 μH to 21 μH.

Referring to FIG. 3, a number of amorphous ribbon sheets, for example,six-layer amorphous ribbon sheets 21-26 are laminated and used as a thinmagnetic sheet, and a number of adhesive layers or double-sided tapes 3a-3 f are inserted between the amorphous ribbon sheets 21-26.

That is, when the fine pieces 20 that have been separated at the time ofthe flake treatment and laminating processes maintain the separatepositions, it is required that the adhesive layers or double-sided tapes3 a-3 f should be inserted and laminated between the amorphous ribbonsheets 21-26, so that gaps 20 a between the fine pieces 20 are filledwith the adhesive layers or double-sided tapes 3 a-3 f.

The magnetic field shield sheets 10, 10 a and 10 b according to thepresent invention constitute a quadrangle such as a rectangular orsquare shape which usually corresponds to the battery cells, butconstitute a polygonal shape such as a pentagon, or a circular or ovalshape, and a combination of a rectangular shape and a circular shapepartly. Preferably, the magnetic field shield sheets have shapescorresponding to the shape of a region for which a magnetic fieldshielding action is required.

Further, the magnetic field shield sheet according to the presentinvention may be molded into an annular shape corresponding to asecondary coil of a reception device like a magnetic field shield sheet10 c shown in FIG. 6 according to a third embodiment of the presentinvention, to prevent a phenomenon that the magnetic field shield sheetis magnetized (or saturated) by a magnetic field of a permanent magnet,in the case that the permanent magnet is included at a central portionof a primary coil of a transmission device of a wireless charger.

The magnetic field shield sheet 10 c according to the third embodimentis made in any one of the correspondingly rectangular, circular, andelliptical shape, when the secondary coil is composed of any one of arectangular, circular, and oval shape. In this case, the magnetic fieldshield sheet 10 c is preferably made of a width by about 1-2 mm widerthan that of the secondary coil 6.

The magnetic field shield sheet 10 c according to the third embodimentmay have a structure that an annular thin magnetic sheet 2 b on theupper surface of which an annular protective film 1 a is attached isattached to a release film 4 through an annular double-sided tape 3.

The annular magnetic field shield sheet 10 c is preferably configured byusing a release film 4 of a rectangular shape having an area larger thanthat of the annular magnetic field shield sheet 10 c so as to be easilypeeled off from the release film 4.

Hereinbelow, a method of manufacturing the magnetic field shield sheetaccording to the present invention will be described with reference toFIG. 7.

First, an amorphous ribbon 2 a (of FIG. 10) consisting of an amorphousalloy or nanocrystalline alloy is prepared by a rapidly solidificationprocess (RSP) due to melt spinning (S11), and is cut in a predeterminedlength to then be laminated in a sheet form (S12) so thatpost-processing after a heat treatment can be easily performed.

In the case that the amorphous ribbon 2 a is an amorphous alloy, anultra-thin amorphous ribbon equal to or less than 30 μm made of aFe-based amorphous ribbon, for example, a Fe—Si—B or Fe—Si—B—Co alloy isprepared by the rapidly solidification process (RSP) due to meltspinning, and then a laminated amorphous ribbon sheet is heat-treatedunder no magnetic circumstances for 30 minutes to 2 hours in atemperature range of 300° C. to 600° C., so as to obtain a desiredpermeability (S13).

In this case, since the heat treatment is performed under an atmosphereof a temperature range at which oxidation is not generated even if theFe content of the amorphous ribbon 2 a is high, it is not necessary forthe heat treatment to be done in an atmosphere furnace, but the heattreatment may proceed in air. In addition, even if the heat treatment ismade under an oxidizing atmosphere or a nitrogen atmosphere,permeability of the amorphous ribbon has substantially no difference atthe same temperature condition.

In the case that the heat treatment temperature is less than 300° C.,the permeability higher than a desired permeability is obtained and ittakes a longer time for the heat treatment. In addition, in the case ofexceeding 600° C., the permeability is significantly lowered by anoverheat treatment, to thus fail to obtain a desired permeability.Generally, when the heat treatment temperature is low, it takes a longtime for the heat treatment. In contrast, when the heat treatmenttemperature is high, the heat treatment time is shortened.

Further, in the case that the amorphous ribbon 2 a is made of ananocrystalline alloy, a Fe-based amorphous ribbon, for example, anultra-thin amorphous ribbon equal to or less than 30 μm made of aFe-based amorphous ribbon, for example, a Fe—Si—B—Cu—Nb alloy isprepared by the rapidly solidification process (RSP) due to meltspinning, and then a laminated amorphous ribbon sheet is heat-treatedunder no magnetic circumstances for 30 minutes to 2 hours in atemperature range of 400° C. to 700° C., so as to obtain a desiredpermeability (S13).

In this case, the Fe content of the amorphous ribbon 2 a is equal to ormore than 70 at %. Therefore, if the heat treatment is made in the air,the oxidation is generated and thus the heat treatment atmosphere isundesirable in terms of a visual appearance. Thus, it is preferable thatthe heat treatment should be performed in a nitrogen atmosphere.However, even if the heat treatment is made under an oxidizingatmosphere, permeability of the sheet has substantially no difference atthe same temperature condition.

In this case, when the heat treatment temperature is less than 400° C.,nanocrystalline particles are not sufficiently produced, and a desiredpermeability is not obtained. Further, it takes a longer time for theheat treatment. In addition, in the case of exceeding 700° C., thepermeability is significantly lowered by an overheat treatment. When theheat treatment temperature is low, it preferably takes a long time forthe heat treatment. In contrast, when the heat treatment temperature ishigh, the heat treatment time is preferably shortened.

Further, a thickness of the amorphous ribbons 2 a of the presentinvention is in the range of 15 to 35 μm, and permeability of theamorphous ribbon 2 a increases in proportion to the thickness of theribbon.

Furthermore, when the heat treatment is made, the amorphous ribbon isstrong for embrittlement. Accordingly, when a flake treatment process iscarried in a subsequent step, the flake treatment process can be easilymade.

Subsequently, a layer or a multi-layer of the amorphous ribbon 2 a whoseheat treatment has been made are used as many as a desired number oflayers, and then a flake treatment process is performed in a state wherea double-sided tape 3 is attached (S14) in which the protective film 1is attached to one side of double-sided tape 3 and the release film 4 isattached to the other side of the double-sided tape 3.

The flake treatment process is performed to make a laminate sheet 100where the protective film 1, the amorphous ribbon 2 a, the double-sidedtape 3, and the release film 4 are sequentially stacked, passed throughfirst and second flake devices 110 and 120, for example, as shown inFIGS. 8 and 9, to thereby allow the amorphous ribbon 2 a to be separatedinto a number of fine pieces 20. In this case, as shown in FIG. 10, theseparated fine pieces 20 maintain a state of being separated by firstand second adhesive layers 12 and 31 bonded to both side surfaces of theamorphous ribbon 2 a.

For example, as shown in FIG. 8, an available flake device 110 mayconsist of a metal roller 112 on the outer surface of which a pluralityof irregularities 116 are formed, and a rubber roller 114 that isdisposed in opposition to the metal roller 112. As shown in FIG. 9, asecond flake device 120 may be composed of a metal roller 122 on theouter surface of which a plurality of spherical balls 126 are mounted,and a rubber roller 124 that is disposed in opposition to the metalroller 122.

Thus, when the laminate sheet 100 is passed through the first and secondflake devices 110 and 120, the amorphous ribbon 2 a is separated intothe fine pieces 20 and gaps 20 a are formed between the fine pieces 20,as shown in FIG. 10.

Since the fine pieces 20 of the amorphous ribbon 2 a are formed to havea size of a range of several tens micrometers (μm) to 3 milimeters (mm),a reverse magnetic field is made to increase to thereby remove ahysteresis loss and to thus heighten a uniformity of the permeability ofthe sheet.

Further, the flake treatment process of the amorphous ribbon 2 a mayreduce the surface area of the fine pieces 20 and prevent a heatgeneration problem caused by an eddy current that is produced by analternating-current magnetic field.

The flake treated laminate sheet 200 has the gaps 20 a between finepieces 20. Thus, when the water is penetrated into the gaps 20 a, theamorphous ribbon is oxidized and the appearance of the amorphous ribbonis poor and the shield performance is degraded.

Further, in the case that only a flake treatment process is performed,the fine pieces 20 are in contact with each other along the flow of thefine pieces 20, to accordingly increase the size of the fine pieces 20and to thus cause a problem that the eddy-current loss increases.

Furthermore, the flake treated laminate sheet 200 may havenon-uniformity caused on the surface of the sheet during performing theflake treatment process, and stabilization of the flake treated ribbonis needed.

Thus, the flake treated laminate sheet 200 undergoes a laminatingprocess for flattening, slimming, and stabilization of the sheet 200,while simultaneously filling the adhesive into the gaps 20 a of the finepieces 20 (S15). As a result, water penetration is prevented, and at thesame time all sides of the fine pieces 20 are surrounded by theadhesive, to thereby separate the fine pieces 20 from one another andreduce the eddy current.

As shown in FIG. 11, a laminating device 400 for the laminating processmay employ a roll press type including a first pressing roller 210 and asecond pressing roller 220 that is disposed at a predetermined distancefrom the first pressing roller 210, between which the flake treatedlaminate sheet 200 passes. As shown in FIG. 12, a laminating device 500for the laminating process may employ a hydraulic press type including alower pressing member 240 and an upper pressing member 250 that isvertically movably disposed on the upper side of the lower pressingmember 240.

When the flake treated laminate sheet 200 is heated at room temperatureor at a temperature of 50° C. to 80° C., and then is passed through thelaminating device 400 or 500, a first adhesive layer 12 of theprotective film 1 is pressed, while some of the adhesive of the firstadhesive layer 12 are introduced into the gaps 20 a to seal the gaps 20a. Simultaneously, the double-sided tape 3 is pressed, while some of theadhesive of the second adhesive layer 31 are introduced into the gaps 20a to seal the gaps 20 a.

Here, the first adhesive layer 12 and the second adhesive layer 31 maybe formed by using an adhesive that can be deformed at the time of beingpressed at room temperature, or may be formed by using a thermoplasticadhesive that can be thermally deformed by applied heat.

In addition, the first adhesive layer 12 and the second adhesive layer31 preferably have a thickness of at least 50% when compared to thethickness of the amorphous ribbon so as to sufficiently fill the gaps 20a between the fine pieces 20.

Further, the interval between the first pressure roller 210 and thesecond pressure roller 220 and the interval between the upper pressingmember 250 and the lower pressing member 240 when the upper pressingmember 250 is in a lowered state, are preferably formed of a thicknessof 50% or less when compared to the thickness of the laminate sheet 200,so that the adhesive of the first adhesive layer 12 and the secondadhesive layer 31 can be introduced into the gaps 20 a.

Any device of performing the pressing of the laminate sheets 100 and 200and the flake treatment process, can be used in the present invention.

As shown in FIG. 13, when the laminating process is completed, anelectromagnetic wave absorbing sheet 10 according to the presentinvention may have a structure that the first adhesive layer 12 and thesecond adhesive layer 31 partially fill the gaps 20 a between the finepieces 20 at a state where the amorphous ribbon 2 a is separated intothe fine pieces 20, to thereby prevent the oxidation and the flow of theamorphous ribbon 2 a.

Finally, the magnetic field shield sheet 10 having undergone thelaminating process is stamped into the size and shape necessary forplace and use for electronic devices so as to be produced into products(S16).

In the case that six sheets of the amorphous ribbon sheets 21-26 arestacked as the thin magnetic film, in the present invention, as shown inFIG. 3, a thickness of the magnetic filed shield sheet 10 b includingthe protective film 1 and the release film 4 is 212 μm before thelaminating process is performed, but the former is 200 μm afterlaminating process is performed.

In the embodiment, it has been described with respect to the case that asheet of the protective film 1 is adhered to one side of the magneticsheet 2 and then the flake treatment process and the laminating processare executed, but the protective film 1 may be damaged by the flaketreatment process. Thus, preferably, a temporary protective film forprotecting the protective film 1 is attached on top of the protectivefilm 1 before performing a treatment process, and then the temporaryprotective film on the surface of the magnetic sheet 2 is peeled off andremoved after completion of the treatment process.

Humidity Test

humidity test was conducted for 120 hours at temperature of 85° C. andhumidity of 85% with respect to the magnetic field shield sheet 10obtained in accordance with the invention and the laminate sheet 200that has undergone the flake process but does not pass through thelamination process.

As a result, as shown in FIG. 14A, in the case of the laminate sheet 200whose only the flake-treatment was processed, it can be seen that wateris penetrated into the gaps between fine pieces when the amorphousribbon has been separated into a large number of fine pieces and thenthe amorphous ribbon is oxidized, and thus the appearance of theamorphous ribbon was changed. However, it can be seen that the magneticfield shield sheet 10 in accordance with the present invention shows theappearance that does not change as shown in FIG. 14B.

The magnetic field shield sheet according to the present invention maybe configured by using dissimilar materials illustrated in FIGS. 15a and15b as a thin film magnetic sheet.

As shown in FIG. 15A, a thin film magnetic sheet 35 can be configured ina hybrid form in which a bonding layer 35 c is inserted and combinedbetween a first magnetic sheet 35 a of a high permeability and a secondmagnetic sheet 35 b of a permeability lower than that of the firstmagnetic sheet 35 a.

An amorphous ribbon sheet consisting of the above-described amorphousalloy or nanocrystalline alloy, a permalloy sheet having an excellentsoft magnetic characteristic, or a MPP (Moly Permalloy Powder) sheet canbe used as the first magnetic sheet 35 a.

The second magnetic sheet 35 b may be formed of a polymer sheetconsisting of a magnetic powder of a high permeability such as anamorphous alloy powder, soft magnetic powder, or a sendust, and a resin.

In this case, the amorphous alloy powder has a composition selected fromthe group consisting of for example, Fe—Si—B, Fe—Si—B—Cu—Nb, Fe—Zr—B andCo—Fe—Si—B, and preferably is formed of an amorphous alloy powdercomprising one or more amorphous alloys.

Further, in the case that both a near field communications (NFC)function and a wireless charging function are employed in a portableterminal, the hybrid-type thin film magnetic sheet 35 is formed by usingan amorphous ribbon sheet and a ferrite sheet with low frequencydependence that are laminated and stacked one over another, as the firstand second magnetic sheets 35 a and 35 b, as shown in FIG. 15A.Accordingly, it is possible to solve both the near field communications(NFC) function and the wireless charging function by using the ferritesheet for the magnetic field shield for the NFC and by using theamorphous ribbon sheet for the wireless charger.

Further, in the case that both a near field communications (NFC)function and a wireless charging function are employed in a portableterminal, the hybrid-type thin film magnetic sheet 35 may be formed byusing a certain area of an amorphous ribbon sheet at a center of thehybrid-type thin film magnetic sheet 35, as a first magnetic sheet 35 a,and by combining a second annular magnetic sheet 35 b that surrounds thewhole of the first magnetic sheet 35 a on the outside of the firstmagnetic sheet 35 a into a ferrite loop, as shown in FIG. 15B. That is,the ferrite having a relatively smaller permeability than the amorphoussheet is formed in a loop form and is arranged in the outer block of theamorphous sheet.

Meanwhile, a structure that the magnetic field shield sheet according tothe present invention is employed in a reception device for a wirelesscharger will be described below with reference to FIGS. 16 and 17.

FIG. 16 is an exploded perspective view showing a structure that amagnetic field shield sheet according to the present invention isapplied to a reception device for a wireless charger, and FIG. 17 is anexploded perspective view showing that the reception device for awireless charger of FIG. 16 is assembled with a battery cover andcoupled with a portable terminal.

Referring to FIG. 16, when a magnetic field shield sheet according tothe present invention is applied to a reception device for a wirelesscharger, a receiving-side secondary coil 6 of the wireless charger isattached on an upper portion of a protective film of a magnetic fieldshield sheet 10 by using a double-sided tape 30 b. In addition, afinishing material (not shown) is adhered to an adhesive layer 33 of thedouble-sided tape 30 b that is exposed by removing the release film 4from the lower portion of the magnetic field shield sheet 10, forexample, as shown in FIG. 13.

Further, instead of the method for assembling the antenna, it is alsopossible to attach the secondary coil 6 of the wireless charger to thedouble-sided tape 3 after having removed the release film 4 of themagnetic field shield sheet 10.

As shown in FIG. 17, an assembly of the secondary coil 6 and themagnetic field shield sheet 10 is attached to a battery cover 5 for aportable terminal device 101 by using a double-sided tape 30 a. Then,when the battery cover 5 is coupled to the mobile terminal device 101,the magnetic field shield sheet 10 is used in the form of a cover of thebattery 7.

An assembly position of the magnetic field shield sheet 10 may bedisposed in the outside of the battery, or may be disposed in awell-known method.

The secondary coil 6 having a well-known structure may be also used. Forexample, the secondary coil 6 may be configured to have a spiral coil 6a made of any one of a rectangular, round, oval shape on a substratemade of a synthetic resin 6 b such as a polyimide (PI), as shown in FIG.16.

The secondary coil 6 may be assembled into a thin film structure bydirectly forming the spiral coil 6 a on a single adhesive sheet thatserves as an insulating layer in place of the synthetic resin substrate6 b and the double-sided tape 30 b, for example, a double-sided tape ina transfer manner.

In this case, the spiral coil 6 a that plays a role of receiving powerwirelessly, may be also formed by winding a general coil in the form ofa planar inductor to then be adhered on a substrate.

Meanwhile, the portable mobile terminal device 101 includes a rectifier(not shown) that rectifies an AC voltage generated in the spiral coil 6a of the secondary coil 6 into a direct-current (DC) voltage in theinside of a main body, in which the rectified DC voltage is charged intoa battery (i.e., a secondary cell 7).

As described above, in the case that an assembly of the secondary coil 6and the magnetic field shield sheet 10 is provided in the battery cover5 of the portable terminal device 101, an influence upon the portableterminal device 101 by an AC magnetic field generated when a wirelesscharging function is implemented in a non-contact (wireless) manner inthe mobile terminal device 101 can be blocked and electromagnetic wavesrequired to perform the wireless charging function can be absorbed.

That is, as shown in FIG. 13, the magnetic field shield sheet 10according to the present invention includes a multi-layer magnetic sheet2 that is flake treated and separated into a plurality of fine pieces20, to thereby increase a quality factor (Q), and to thus increaseelectric power transmission efficiency. In addition, the magnetic fieldshield sheet 10 is flake treatment processed, to thereby reduce asurface area of the ribbon and to accordingly prevent a heat generationproblem caused by the eddy currents generated by the AC magnetic field.

As a result, the magnetic flux generated from the primary coil of thetransmission device is blocked from being interlinked with a circuitboard of the portable terminal device and the battery (or a secondarybattery) 7 to thus suppress heat generation.

Meanwhile, FIG. 18 is a plan view showing a dual-antenna structure inwhich an antenna for near field communications (NFC) and an antenna fora wireless charger are integrally formed by using a flexible printedcircuit board (FPCB).

A dual antenna 40 that performs both the NFC function and the wirelesscharging function is preferably implemented by using a flexible printedcircuit board (FPCB) having a double-sided substrate structure. However,the dual antenna according to the present invention is not limitedthereto, but a different type of an antenna structure may be used.

Referring to FIG. 18, a dual antenna 40 is configured to include, forexample, a NFC antenna coil 41 and a wireless charger antenna coil 43that are formed together on a substrate 49. The substrate 49 may beconfigured by using, for example, a double-sided adhesive tape, and theNFC antenna coil 41 and the wireless charger antenna coil 43 are formedon the adhesive substrate 49 by using a transfer method.

Since the NFC antenna coil 41 has a higher frequency band than thewireless charger antenna coil 43, the NFC antenna coil 41 is formed tohave a conductive pattern of a rectangular shape of a fine line widthalong the outside of the substrate 49. In addition, since the wirelesscharger antenna coil 43 requires the power transmission and uses a lowerfrequency band than the NFC antenna coil 41, the wireless chargerantenna coil 43 is formed in the inside of the NFC antenna coil 41 tohave a conductive pattern of a substantially elliptical shape of a linewidth wider than the width of the NFC antenna coil 41.

The dual antenna 40 is configured to have a pair of terminal strips 41 aand 41 b, and 43 a and 43 b, which are disposed on a projection of thesubstrate 49 respectively extended at one side of the NFC antenna coil41 and the wireless charger antenna coil 43.

The outer line of the NFC antenna coil 41 is directly connected to afirst terminal block 41 a, and the inner line thereof is connected to asecond terminal block 41 b via a terminal connecting pattern (not shown)that is formed on the rear surface of the substrate 49 throughconductive throughholes 45 a and 45 b.

Similarly, the outer line of the wireless charger antenna coil 43 isconnected to a third terminal block 43 a via a terminal connectingpattern (not shown) that is formed on the rear surface of the adhesivesubstrate 49 through conductive throughholes 47 a and 47 b, and theinner line thereof is connected to a fourth terminal block 43 b via aterminal connecting pattern (not shown) that is formed on the rearsurface of the substrate 49 through conductive throughholes 47 c and 47d.

A protective film for protecting an antenna coil pattern such as, forexample, PSR (Photo Solder Resist) is preferably formed on the surfaceof the substrate 49.

In the case that both the NFC function and the wireless chargingfunction are employed, as described above, a shield sheet employing ahybrid type magnetic sheet of FIGS. 15A and 15B may be used.

Hereinafter, embodiments of the present invention will be described inmore detail. However, the following examples of the present inventionare nothing but illustrative and the scope of the present invention isnot limited thereto.

Examples 1-4 and Comparative Examples 1-3

Electrical Characteristics of Magnetic Field Shield Sheets

No magnetic field shield sheet was used (Comparative Example 1). Amagnetic field shield sheet using one amorphous ribbon sheet that wasnot heat treated (Comparative Example 2), a magnetic field shield sheetusing one nanocrystalline ribbon sheet that was heat treated(Comparative Example 3), a magnetic field shield sheet using onenanocrystalline ribbon sheet that was heat treated and flake treated(Example 1), a magnetic field shield sheet using two nanocrystallineribbon sheets that were heat treated and flake treated (Example 2), amagnetic field shield sheet using three nanocrystalline ribbon sheetsthat were heat treated and flake treated (Example 3), and a magneticfield shield sheet using four nanocrystalline ribbon sheets that wereheat treated and flake treated (Example 3), were prepared respectively.

An amorphous alloy ribbon sheet applied for a shield sheet was preparedby comprising: making an amorphous ribbon made of aFe_(73.5)Cu₁Nb₃Si_(13.5)B₉ alloy in a thickness of 25 μm by a rapidsolidification method (RSP) due to melt spinning; cutting the amorphousribbon in a sheet form and heat treating the cut sheet at 580° C., underno magnetic field, in a nitrogen (N2) atmosphere, for 1 hour, to therebyobtain the amorphous ribbon sheet; inserting the amorphous ribbon sheetbetween a protective film of 10 μm thick using a polyethyleneterephthalate (PET) base member and a double-sided tape (with a releasefilm excluded) of 10 μm thick using a PET base member, to therebyprepare a laminate sheet; and performing flake treatment and laminationtreatment processes respectively by using a flake treatment processingdevice of FIG. 8 and a laminating device of FIG. 11. When two or morenanocrystalline ribbon sheets are laminated, acrylic adhesive layers of12 μm formed on both sides of the PET film were used as double-sidedtapes inserted between the nanocrystalline ribbon sheets.

To examine an influence upon a secondary coil when a prepared shieldsheet was used in a wireless charger, a circular planar coil having aninductance of 12.2 pH and a resistance of 237 mΩ was used as a secondarycoil bonded to the shield sheet, that is, as a measuring coil. Then, themeasuring coil was connected to an LCR meter to measure the inductance(L), capacitance (C), and resistance (R), and then the LCR meter waslocated on the shield sheet. Then, a certain pressure was applied to themeasuring coil by placing a rectangular parallelepiped having a weightof about 500 g on the measuring coil, and setting values of the LCRmeter were set to be 100 kHz and 1 V. Then, inductance (Ls),magnetoresistance (Rs), impedance (Z), and coil quality factor (Q) weremeasured and represented in the following Table 1.

TABLE 1 Number of Ribbons tested ribbons Ls(μH) Rs(mΩ) Z(Ω) QComparative Example 0 12.08 245 7.59 30.9 1 (No Sheet) ComparativeExample 1 EA 17.91 1020 11.3 11.03 2(Non-heat treated ribbon)Comparative Example 1 EA 21.74 605 13.67 22.53 3(Heat treated ribbon)Example 1(Heat and 1 EA 21.52 442 13.52 30.5 flake treatment) Example2(Heat and 2 EA 21.54 355 13.54 38 flake treatment) Example 3(Heat and 3EA 21.56 327 13.55 41.4 flake treatment) Example 4(Heat and 4 EA 21.7308 13.64 44.2 flake treatment)

As can be seen from Table 1, in the case of a shield sheet using aribbon which was not heat treated (Comparative Example 2), the magneticpermeability was low. Thus, since the inductance (Ls) of the secondarycoil was small, and the electric resistance of the ribbon was low, themagnetoresistance (Rs) was large and the coil quality factor (Q) wasremarkably low.

In the case of a shield sheet using a ribbon sheet which was heattreated (Comparative Example 3), the magnetic permeability was high.Thus, since the inductance (Ls) of the secondary coil was large, and theelectric resistance of the ribbon sheet was high through nanocrystallinemicrostructures produced in the ribbon sheet by the heat treatment, themagnetoresistance (Rs) was greatly low when compared with before theheat treatment and thus the coil quality factor (Q) was greatly elevatedwhen compared with before the heat treatment.

Further, in the case of a shield sheet using a ribbon sheet which washeat treated and flake treated (Example 1), since the inductance (Ls) ofthe secondary coil was not greatly changed, and the magnetoresistance(Rs) was greatly low when compared with when the flake treatment was notperformed, the coil quality factor (Q) was greatly elevated.

Furthermore, when compared to Example 1, the higher the number ofstacked sheets of the ribbon sheets may increase, the coil qualityfactor (Q) was greatly increased.

As described above, when the shield sheets according to the presentinvention are used in the wireless charger, the inductance (Ls) and thecoil quality factor (Q) of the secondary coil is increased, and themagnetoresistance (Rs) is decreased. Accordingly, a transmissionefficiency of the magnetic flux transmitted from the transmission devicefor the secondary coil for the wireless charger can be increased.

Examples 5-8 and Comparative Example 1

Power Transmission Efficiency of Magnetic Field Shield Sheets

The magnetic field shield sheets of Examples 5 to 7 were prepared into arectangular shape in the same manner as in Examples 1 to 4. However, thenumber of nanocrystalline ribbon sheets laminated in the magnetic fieldshield sheets was changed into 6, 9, or 12. The magnetic field shieldsheet of Example 8 was different from that of Example 6, in a point thatthe former was configured by making the shape of the latter (the numberof nanocrystalline ribbon sheets was six) in the same annular shape asthat of the secondary coil.

Concerning Comparative Example 1 (in the case that no magnetic fieldshield sheet is used), and magnetic field shield sheets of Examples 5 to8, respectively, as shown in FIG. 19, a separator sheet of paper 9 of0.5 mm thick was placed on the upper portion of the transmission device8 of the wireless charger, and then the magnetic field shield sheet 10and the reception device with which the secondary coil 6 was assembledwere placed on a lithium ion battery 7. In this state, voltage (V) andcurrent (mA) applied to the primary coil of the transmission device 8,and voltage (V) and current (mA) applied to the secondary coil 6 of thereception device were measured and shown in the following Table 2, basedon which the power transmission efficiency was calculated.

TABLE 2 Transmission Reception device device Ribbons tested V mA V mAEfficiency(%) Comparative Example 1 19 188 4.87 520 70.895857 (No Sheet)Example 5(six rectangular 19 205 4.87 521 65.141720 ribbons) Example6(nine 19 194 4.87 521 68.835323 rectangular ribbons) Example 7(twelve19 190 4.87 521 70.284488 rectangular ribbons) Example 8(six coil-shaped19 192 4.87 521 69.552357 ribbons)

In the case that a transmission device of a wireless charger employed apermanent magnet, according to the conventional art, a thickness of ashield sheet using a ferrite sheet due to a DC magnetic field of thepermanent magnet should have been at least 0.5 T in order to perform anoptimum wireless charging operation.

With reference to Table 2 above, as shown in Examples 5 to 7, in thecase that the shield sheet, that is, the shape of the nanocrystallineribbon sheet was rectangular, it could be seen that twelve or morenanocrystalline ribbon sheets were laminated in order to havesubstantially the same power transmission efficiency as that of thereception device of Comparative Example 1 having no shield sheet.

Further, in the case that twelve nanocrystalline ribbon sheets were usedas in Example 7 of the present invention, permeability is high, and thussimilar properties to the ferrite or the polymer sheet were obtainedeven at a thickness of 0.3 T lower than 0.5 T which was exhibited in thecase of the conventional shield sheet using a ferrite sheet.

Further, in the case of making the shape of the magnetic field shieldsheet (the number of nanocrystalline ribbon sheets was six) in the sameannular shape as that of the secondary coil as in Example 8, it could beseen that substantially the same power transmission efficiency as thatof Example 7 was exhibited even though the number of the nanocrystallineribbon sheets used was ½ of Example 7 (the number of nanocrystallineribbon sheets was twelve).

As a result, in the case of making the shape of the magnetic fieldshield sheet in the same annular shape as that of the secondary coil asin Example 8, the number of the nanocrystalline ribbon sheets used wasreduced into ½, thereby lowering production costs, and further slimmingthickness of products.

This result exhibited almost the same even though the shape of thesecondary coil of the reception device and the shape of the magneticfield shield sheet corresponding to the shape of the secondary coil werechanged into the different shapes.

Temperature Characteristics

The magnetic field shield sheet according to Example 8 was set as shownin FIG. 19, and temperatures of the battery and the nanocrystallineribbon sheet of the magnetic field shield sheet were measured in unitsof an interval of 30 minutes for the charging time from 30 minutes to 4hours 30 minutes, and the results were shown in Table 3.

TABLE 3 Charging time Temperature of Temperature of interval battery (°C.) ribbon sheet (° C.) 0.5 hours 29.5 30 1.0 hour 30 30 1.5 hours 30.530.5 2.0 hours 30.5 30.5 2.5 hours 30.5 31 3.0 hours 30.5 31 3.5 hours30.5 31 4.0 hours 30.5 31 4.5 hours 30.5 31

In general, if a secondary battery such as a lithium ion battery 7 isover 40° C. when a wireless charging operation is made, safety problemsmay arise.

When the shield sheet of the present invention is applied for a wirelesscharger, as described in Table 3, the temperatures of the battery andthe shield sheet did not rise even in the course of time, but maintained30° C. or so. Thus, it could be seen that safety was ensured.

Example 9

An amorphous alloy ribbon sheet applied for a shield sheet was preparedby comprising: making an amorphous ribbon made of a Fe₆₇B₁₄Si₁Co₁₈ alloyin a thickness of 25 μm by a rapid solidification method (RSP) due tomelt spinning; cutting the amorphous ribbon in a sheet form and heattreating the cut sheet at 487° C., 459° C., and 450° C., under nomagnetic field, for 1 hour, respectively, to thereby obtain theamorphous ribbon sheet; inserting the amorphous ribbon sheet between aprotective film of 10 μm thick using a polyethylene terephthalate (PET)base member and a double-sided tape (with a release film excluded) of 10μm thick using a PET base member, to thereby prepare a laminate sheet;and performing flake treatment and lamination treatment processesrespectively by using a flake treatment processing device of FIG. 8 anda laminating device of FIG. 11.

Here, one to nine nanocrystalline ribbon sheets to be used in a laminatesheet were laminated for heat treatment temperatures, and double-sidedtapes were inserted between the amorphous ribbon sheets. The inductance(permeability) and the charging efficiency of each of the amorphousribbon sheets for the heat treatment temperatures were measured andshown in Table 4.

TABLE 4 Charging efficiency (%) Inductance 1 2 3 4 5 6 7 8 9(permeability) sheet sheets sheets sheets sheets sheets sheets sheetssheets 13 μH 56 61 65.6 65.8 67.1 68.4 68.9 69.1 Inoperable 15 μH 59.265.8 68 68.4 68.6 69.1 69.1 69.3 68.9 18 μH 57 63.6 66.3 68 68.2 68.969.1 69.1 68.9

In the result of heat treating each amorphous ribbon sheet at 487° C.,459° C., and 450° C. for one hour under no magnetic field, theinductance (permeability) of each sheet was decreased into 13 μH, 15 μH,18 μH with the increase in the heat treatment temperature.

The charging efficiency for the inductance of each sheet was the highestin the case that the inductance (permeability) of the sheet that washeat treated at 459° C. was 15 μH. As the number of laminated amorphousribbon sheets was increased from one to eight, the charging efficiencywas also increased proportionally with the number of the sheets. In thecase that about 4 sheets were laminated, a saturation phenomenonoccurred, and in the case of exceeding eight sheets, the chargingefficiency was decreased.

Example 10

The maximum charging efficiency of the laminated sheets for the numberof laminated sheets was measured by using the amorphous ribbon sheet ofthe inductance (permeability) of 15 μH, and the results were shown inTable 5.

The maximum charging efficiency was obtained in the state where value ofa time constant of the reception device was adjusted to make theefficiency set to a maximum value based on value of the inductance ofthe reception device of the wireless charger, that is, the secondarycoil.

TABLE 5 Maximum charging efficiency (%) Permeability 1 sheet 2 sheets 3sheets 4 sheets 15 μH 61.3 68.7 71.1 71.9

Referring to Table 5, the efficiency was increased according to thenumber of laminated amorphous ribbon sheets, and the maximum chargingefficiency was 71.9% in the highest in the case of four sheets.

As described above, the present invention greatly reduces a loss due toeddy currents by a flake treatment process of an amorphous ribbon, tothereby block an effect of a magnetic field influencing upon a main bodyand a battery of a portable mobile terminal device and simultaneously toincrease a quality factor (Q) of a secondary coil, and to thus exhibitexcellent electric power transmission efficiency.

In addition, the present invention fills a gap between fine pieces of anamorphous ribbon through a flake treatment process of the amorphousribbon and then a compression laminating process with an adhesive, tothereby prevent water penetration, and simultaneously surrounds allsurfaces of the fine pieces with an adhesive (or a dielectric) to thusmutually isolate the fine pieces to thereby promote reduction of eddycurrents and prevent shielding performance from falling.

Moreover, the present invention establishes a shape of a shield sheetinto a shape similar to that of a coil of a receiving device for awireless charger, to thereby exhibit a high power transmissionefficiency or equal power transmission efficiency while loweringthickness of the magnetic field shield sheet to be equal to or less than0.3 mm, even though a small number of nanocrystalline ribbons are used.

In addition, the present invention sequentially performs a flaketreatment process and a laminating process by using a roll-to-rollmethod, to thereby achieve a sheet molding process to thus maintainoriginal thickness of the sheet and to thus exhibit high productivityand inexpensive manufacturing costs.

The embodiments of the present invention have been described withrespect to the case that a wireless charger is applied to a portableterminal device, but it is apparent to one of ordinary skill in the artthat the present invention can be applied to all portable terminaldevices providing a wireless charging function in a non-contact(wireless) manner.

As described above, the present invention has been described withrespect to particularly preferred embodiments. However, the presentinvention is not limited to the above embodiments, and it is possiblefor one who has an ordinary skill in the art to make variousmodifications and variations, without departing off the spirit of thepresent invention. Thus, the protective scope of the present inventionis not defined within the detailed description thereof but is defined bythe claims to be described later and the technical spirit of the presentinvention.

INDUSTRIAL APPLICABILITY

A magnetic field shield sheet for a wireless charger according to thepresent invention may be applied to a variety of portable electronicdevices including a portable terminal device, to thereby block aninfluence upon the portable terminal device by AC and DC magnetic fieldsthat are generated when a wireless charging function is implemented in anon-contact (wireless) manner, and to thereby assist the magnetic fieldshield sheet for a wireless charger to absorb electromagnetic wavesnecessary for the wireless charging function.

The invention claimed is:
 1. A magnetic field shield sheet for awireless charger, the magnetic field shield sheet comprising: a thinmagnetic sheet separated into a plurality of pieces by a flake-treatmentprocess; and an adhesive member adhered on one surface of the thinmagnetic sheet such that the adhesive member is adhered to the pluralityof pieces; wherein at least parts of the pieces are mutually isolated,and at least parts of gaps among the plurality of pieces are filled byan adhesive of the adhesive member.
 2. The magnetic field shield sheetfor a wireless charger of claim 1, wherein the adhesive member is adouble-sided tape comprising a base member.
 3. The magnetic field shieldsheet for a wireless charger of claim 1, wherein the adhesive member isa no-base type tape, the thin magnetic sheet is adhered on one surfaceof the adhesive member, and a release film is separably adhered on theother surface of the adhesive member.
 4. The magnetic field shield sheetfor a wireless charger of claim 1, further comprising a protectivemember adhered on another surface of the thin magnetic sheet.
 5. Themagnetic field shield sheet for a wireless charger of claim 1, wherein athin ribbon made of an amorphous alloy or nanocrystalline alloy is usedas the thin magnetic sheet.
 6. The magnetic field shield sheet for awireless charger of claim 1, wherein the magnetic field shield sheet isapplied to a reception device of a wireless charger having a permanentmagnet in a transmission device, and wherein the thin magnetic sheetcomprises 2 to 8 layers of laminated sheets made of a Fe-based amorphousalloy, and an adhesive layer is inserted among the laminated sheets. 7.The magnetic field shield sheet for a wireless charger of claim 1,wherein the magnetic field shield sheet is applied to a reception deviceof a wireless charger having a permanent magnet in a transmissiondevice, and wherein the thin magnetic sheet comprises 4 to 12 layers oflaminated sheets made of a nanocrystalline alloy, and an adhesive layeris inserted among the laminated sheets.
 8. The magnetic field shieldsheet for a wireless charger of claim 1, wherein the magnetic fieldshield sheet is applied to a reception device of a wireless chargerhaving no permanent magnet in a transmission device, and wherein thethin magnetic sheet comprises 2 to 4 layers of laminated sheets made ofa Fe-based amorphous alloy or a nanocrystalline alloy, and an adhesivelayer is inserted among the laminated sheets.
 9. The magnetic fieldshield sheet for a wireless charger of claim 1, wherein the magneticfield shield sheet is formed of a shape corresponding to a secondarycoil provided on the reception device of the wireless charger.
 10. Areception device for a wireless charger that charges a secondary batteryfrom a transmission device for the wireless charger, the receptiondevice comprising: a coil unit that receives a wireless signaltransmitted from the transmission device; and a magnetic field shieldsheet that is disposed between the coil unit and the secondary battery,wherein the magnetic field shield sheet comprises: a thin magnetic sheetseparated into a plurality of pieces by a flake-treatment process; andan adhesive member adhered on one surface of the thin magnetic sheetsuch that the adhesive member is adhered to the plurality of pieces;wherein at least parts of the pieces are mutually isolated, and at leastparts of gaps among the plurality of pieces are filled by an adhesive ofthe adhesive member.
 11. The reception device for a wireless charger ofclaim 10, wherein the coil unit and an antenna coil for near fieldcommunications (NFC) are formed on a single substrate.